Does Current Scientific Evidence Support a Link Between Light at Night and Breast Cancer Among Female Night-Shift Nurses?: Review of Evidence and Implications for Occupational and Environmental Health Nurses

Abstract

Breast cancer is increasingly prevalent in industrialized regions of the world, and exposure to light at night (LAN) has been proposed as a potential risk factor. Epidemiological observations have documented an increased breast cancer risk among female night-shift workers, and strong experimental evidence for this relationship has also been found in rodent models. Indirect support for the LAN hypothesis comes from studies involving blind women, sleep duration, bedroom light levels, and community nighttime light levels. This article reviews the literature, discusses possible mechanisms of action, and provides recommendations for occupational health nursing research, practice, and education. Research is needed to further explore the relationship between exposure to LAN and breast cancer risk and elucidate the mechanisms underlying this relationship before interventions can be designed for prevention and mitigation of breast cancer.

Melatonin: a possible link between the presence of artificial light at night and reductions in biological fitness

“…Evidence documenting the physiological impact of LAN comes largely from correlational studies of vertebrate (often human) health. A recent focus has been on links between the intensity of LAN and an increased risk of cancer, immune suppression and heart disease observed in shift workers, a group with frequently chronic exposure to high-intensity night lighting [19][20][21][22]. Human studies are typically correlational, but similar carcinogenic and immunosuppressant effects of artificial night lighting have been observed from laboratory experiments on mice and rats [23][24][25][26], although immune-enhancing effects of dim night lighting have also been reported [27].…”

Relationship between Night Shifts and Risk of Breast Cancer among Nurses: A Systematic Review

“…Once the evaluation of these studies was carried out, those that met the pre-established inclusion criteria were selected, with a total of 12 records meeting these requirements (see Table 3 ). Following this process, and as the last phase of selection, these 12 studies met the quality criteria [ 19 ] established in the critical reading phase [ 2 , 4 , 5 , 6 , 7 , 8 , 9 , 13 , 14 , 15 , 21 , 29 ] ( Table 4 ). The flowchart for this study is presented in Figure 1 .…”

“…Those who exceeded all the criteria were given a positive sign (+) and those who did not, a negative one (−), thus being excluded. The inclusion criteria list can be seen in Table 3 [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ].…”

“…If metastasis is diagnosed, treatment seeks to improve or maintain the quality of life and increase the expectancy of survival of the person, having a palliative character. Although the knowledge of its etiology in recent years has made substantial progress, strongly relating it to multiple factors such as aging, unhealthy lifestyles, or changes in reproductive patterns, there are few revelations regarding occupational risk factors [ 1 , 2 , 3 ].…”

“…People doing night shift work are currently increasing around the world, especially in industrialized countries. This is because more and more regions of the world are adopting the 24-h-a-day model of society, both at home and at work, exposing the population, and especially the female collective, to more hours of artificial light [ 2 , 14 ].…”